Small-sized and high-functionality electronic devices are exceedingly prevailing in recent years. According to this, flexible printed circuit boards are widely used primarily for the small-sized electronic devices such as a notebook-type personal computer, a digital camera, a mobile phone and a game machine.
Information amount handled by the electronic device as above tends to increase in particular and the signal transmission speed of such an electronic device is higher, accordingly. For example, in a case of personal computers, the transmission speed is moving to the standard of 6 Gbps from 2010 to 2011. Importance of taking a signal loss in the transmission line into consideration is increasing.
In addition, the signal amplitude voltage of a signal source tends to be low for transmitting a pulse signal therefrom at high speed in recent years. Owing to this, there becomes a situation in which spike noise derived from the outside or caused by the signal source itself is liable to disturb accurate signal transmission. Typically, a circuit board for performing high-speed signal transmission has transmission lines which have undergone impedance matching. Even with such a circuit board, however, signal loss in the transmission line is increasingly considerable.
Against the spike noise as above, noise control needs to be taken in the transmission lines and/or the electronic device. Specifically, an electromagnetic shield has to be provided for the transmission lines. Nevertheless, to provide the electromagnetic shield, in turn, increases the thickness of the transmission lines. Owing to this, there is a case, for example, where it is difficult to secure the flexibility of the hinge connecting the display to the keyboard of a notebook-type personal computer.
Therefore, to solve the problems of the transmission loss and noise tolerance in high-speed transmission of electric signals, the possible application of the high-speed signal transmission technique that uses an optical fiber and is used in practical applications for long-range signal transmission to the above-mentioned small-sized electronic devices is discussed.
Furthermore, opto-electric hybrid flexible printed circuit boards are known which are obtained by combining a flexible polymer optical waveguide made of organic polymer with a flexible printed circuit board (hereinafter, also briefly “FPC”) in order to apply the high-speed signal transmission technique using light to the hinge of a notebook-type personal computer or the like (for example, refer to Patent Literature 1 to Patent Literature 3).